Evaluation of different tests for detection of Staphylococcus aureus using coagulase (coa) gene PCR as the gold standard.

A total of 288 staphylococcal specimens isolated from different clinical specimens were selected for the evaluation of tests used to detect Staphylococcus aureus. The coagulase (coa) gene PCR was preformed, which confirmed 288 specimens as S. aureus and 51 specimens as coagulase negative staphylococci (CONS). All the specimens were subjected to slide coagulase test, Slidex Staph plus test and tube coagulase test. Sensitivity, specificity, positive predictive value and negative predictive values of were calculated using coa gene PCR as gold standard for the detection ofS. aureus. The tube coagulase test showed very good sensitivity (98.7%), specificity (98.1%), PPV (99.5%) and NPV (94.4%) than other methods. Slidex Staph plus test showed fairly good sensitivity and specificity. Slide coagulase test has good specificity but poor sensitivity. Therefore we recommend that tube coagulase test be done routinely for the detection ofS. aureus in microbiology laboratory.